Uptake of unnatural amino acids into E. coli:: Development of an in vivo method of unnatural protein mutagenesis In vivo introduction of unnatural amino acids into proteins is being developed by engineering of an orthogonal tRNA/aminoacyl-tRNA synthetase (aaRS) pair in E. coli. Selecting for an aaRS capable of accepting an unnatural amino acid as a substrate requires uptake of the amino acid into the cell. Uptake can be asserted by growth in minimal media in the presence of weakly radiolabelled amino acid, followed by extensive washing and scintillation counting of cells adsorbed onto filters. Amino acids taken up by the cell are then candidates for high-incorporation radiolabelling for use in assays of aaRS activity. The amino acids are structurally diverse, including keto, phosphono, and fluorinated amino acids. compounds Program Income: $3397.39